THE GENERATION OF HANDWRITING WITH DELTA-LOGNORMAL SYNERGIES

This paper presents a handwriting generation model that takes advantag e of the asymptotic impulse response of neuromuscular networks to prod uce and control complex two-dimensional synergistic movements. A param etric definition of a ballistic stroke in the context of the kinematic theory of rapid human movements is given. Two types of parameters are used: command and system parameters. The first group provides a repre sentation of the action plan while the second takes into account the t emporal properties of the neuromuscular systems executing that plan. H andwriting is described as the time superimposition of basic discontin uous strokes that results in a continuous summation of delta-lognormal velocity vectors. The model leads to trajectory reconstruction, both in the spatial and in the kinematic domain. According to this new para digm, the angular velocity does not have to be controlled independentl y and continuously; it naturally emerges from the vectorial summation process. Several psychophysical phenomena related to two-dimensional m ovements are explained and analyzed in the context of the model: the s peed/accuracy tradeoffs, spatial scaling, the isochrony principle, the two-thirds power law, effector independence, etc. The overall approac h also shows how basic handwriting characteristics (dimension, slant, baseline, shape, etc.) are affected and controlled using an action pla n made up of virtual targets fed into a neuromuscular synergy that is governed by a delta-lognormal law.